Automated apparatus for welding butt joints between two similarly sized pipes is well known. An apparatus for welding a branch pipe to a main pipe is also known and described in U.S. Pat. No. 4,659,903. This patent teaches a computer controlled welding unit, supported by a gantry crane, and a main pipe positioning machine having opposing servomotor powered cones which lift, support and position a main pipe during the welding operation so that the surface being welded is always relatively level. This apparatus is principally suitable for the automated welding of branch pipe joints required in the construction of pipelines, offshore drilling rig platform structures, bridge supports, and similar large tubular structures.
Modern construction often requires the installation of networks of metal piping, especially for the fire protection systems of building. Building codes generally specify that steel piping be used in the installation of fire sprinkler systems. Fire sprinkler systems usually include one or more header pipes having smaller subheader and/or distribution pipes radially connected at intervals for distributing fire extinguishing fluid throughout the interior of a building. At each point where a branch pipe is required, the headers and/or subheaders must be cut to accommodate a cast iron branch pipe connector in the pipe run, or provided with machined T-junction connectors which are welded in preformed radial holes in the headers and/or subheaders to provide threaded connectors for each branch. Welding machined T-junction connectors to main pipes is cheaper and more efficient than cutting main pipes into sections, threading each end of each section and connecting an expensive cast iron fitting for each branch. There is a disadvantage to using welded T-junctions, however. Traditionally, the welding is done by skilled professional welders. Construction schedules may therefore depend on the availability of experienced welders, and professional welders contribute significantly to the cost of fire sprinkler system installations. There therefore exists a need for a portable automated apparatus for welding T-junction connectors to main pipes and, in particular, for one which may operated by persons without welding experience.
It is an object of the invention to provide a light weight and easily portable apparatus for automatically welding T-junction connectors to a main pipe.
It is a further object of the invention to provide an apparatus for automatically welding T-junction connectors to a main pipe which can be operated by a person with no welding training or experience.
It is yet a further object of the invention to provide an apparatus for automatically welding T-junction connectors to a main pipe which is relatively simple to construct and inexpensive to manufacture.